修复剂注入对地下水污染羽驱动与弥散混合作用机制

The inappropriate injection of the remediation reagent will inevitably ficilitate the migration of contamination plume, and raise pollution risk of surronding groundwater in in-situ groundwater remediation. Based on the theory of hydrogeology and fluid dynamics in porous media, through soil column and soil tank simulation experiment, we studied the mechanism of the interaction between the injection of the remediation reagent and the migration and expansion of the contamination plume, by adopting the casting, slice processing and image acquisition, the tracer observation technique and by using the chemical analysis and the mathematical simulation method. The main contents of this study include:First, this study is going to explore the microscopic and macroscopic structural characteristics of heterogeneous media and their effects on permeability. Second, analyze the physical properties of remediation reagent and the viscosity modification conditions and deformationcharacteristics. Third, study the mechanism and regularity of different injection hydrodynamics (pressure) ,different physical properties of the injection liquid (viscosity, shear thickening or thinning deformation characteristics) and different medium characteristics(pore distribution and lamellar structure) on the migration and expansion of the remediation reagent - contamination plume interface and contamination plume frontal. The purpose is to optimize the injection conditions(injection pressure,physical properties of the injection liquid and medium characteristics) through analyzing the different hydrodynamic dispersion characteristics betweenremediation reagent and contamination plume and exploring the mixing and the hydrodynamic dispersion patterns of remediationreagent in contamination plume,migration and expansion rules of remediation reagent - contamination plume mixing zone. At last, we will build a mathematical model for multi-component migration based on the interaction mechanism of remediationre agent injection and contamination plume extension to provide theoretical and experimental basis for improving the effect of in-situ groundwater remediation engineering.

地下水污染原位修复中修复剂不当注入会促进地下水污染羽迁移扩展，从而加剧周边地下水环境污染风险。本研究以水文地质学和多孔介质流体动力学为基础，通过土柱、土箱模拟实验，采用铸体、薄片加工结合微观图像采集技术，示踪观测、化学测试分析手段和数学模拟方法，研究非均匀介质微观与宏观结构特征及其对渗透性影响，分析修复剂物理特性及粘度改性条件与流变特性，研究不同注入动力（压力）条件、注入液物理特性（粘度、剪切变稠或变稀流变特性）、介质特性（孔隙分布与层状结构）对修复液-污染羽界面、污染羽锋面迁移扩展影响机制与规律，分析修复剂、污染物动力弥散特性与差异，探究修复剂在污染羽中混合、动力弥散规律、修复剂-污染物混合带迁移扩展规律及与污染羽锋作用关系，优化修复剂注入条件（注入压强、注入液物理参数、介质特性参数），建立基于修复液注入对污染羽作用机制多组分运移数学模型，为丰富地下水原位修复技术方法提供理论与实验依据。

地下水原位修复中修复剂的不当注入会促进污染羽的迁移扩展，加剧地下水环境污染风险，而注入的修复剂在污染羽中的弥散、混合状况则直接影响着地下水原位修复的效率。本项目以流体在多孔介质内的流动、渗流特征以及流动动力学为基础，以提高原位注入修复剂与污染羽的混合，减少污染羽的拓展为目标，探究了修复剂注入对污染羽的驱动和两者的差异弥散混合作用机制与规律，取得的主要研究结论和成果如下：.（1）基于图像处理与分析技术，建立了一整套图像摄制装置以及图像分析与处理方法。建立了阈值分割和反卷积分割结合的方法以量化表征修复剂注入溶质羽流的驱动、弥散以及拓展。通过图像法精细的实验分析过程，发现实际修复剂的弥散混合作用应强于污染羽才对修复剂在污染羽中的弥散混合有利、大孔隙介质有利于弥散混合以及流体粘度减弱径向弥散。.（2）揭示了修复剂注入与污染羽之间的相互作用规律，提出了注入时径向羽流前锋、修复剂-污染羽界面在弥散条件下的边界表征方法。注入速率和背景流速的提升在修复剂注入时对修复剂-污染羽界面的混合有利，但也提升了污染羽的拓展，而改变注入方式，同时可以减少污染羽拓展。.（3）在图像细节分析下，探究了在不同注入条件下的混合带变化情况。揭示了非均匀性条件下，溶质的粘弹性和挤出膨胀效应会增强羽流的横向分布，这也是修复剂注入污染羽拓展，界面混合的主要机制。.（4）揭示了反应条件下的注入与羽流拓展的差异。高锰酸钾注入四氯乙烯污染羽的最高浓度界面是随着注入速率、孔隙度、浓度、以及背景流速增大而向注入点方向偏移，四氯乙烯的浓度高峰随注入条件的增加而降低，与保守溶质注入污染羽相比，修复剂-污染羽边界混合增强，但两者接触界面反应速率下降。如果以去除率为标准，结合污染物的拓展，距注入点较近的点混合反应是增强的，较远处则一直的减弱的，即需要结合距离注入点的位置，以及各个背景条件，注入条件的变化来确定注入方式，达到污染羽最优去除。